Dental restorative materials should bond to tooth structure and completely fill a preparation in a tooth. Some materials form strong mechanical bonds to enamel, but bonds to dentin are not sufficient. The objective of this proposal is to develop a new dentin bonding system which will be superior to currently available systems in bond strength and microleakage, yet easy to use clinically. A dentin bonding agent should prevent secondary caries from forming around a restoration. To do this it must have sufficient bond strength to dentin and no microleakage. Preliminary studies showed that an ethylene diamine tetra-acetic acid (EDTA) moiety containing methacrylate was a reasonably good dentin conditioning agent with potential chelating ability. It was synthesized as the addition product of 2 moles of 2-hydroxyethyl methacrylate (HEMA) per mole of EDTA dianhydride. It performed better than commercially available products in bond strength and microleakage tests. However, it proved to be technique-sensitive which is clinically unacceptable. A series of polymerizable EDTA derivatives will be used to synthesize dentin bonding systems. Analogues of EDTA-diEMA will be optimized as a dentin conditioning primer, as a simultaneous conditioner for enamel and dentin, and as a bonding resin. They will compared in shear bond strength and microleakage tests. Scanning electron microscopy will be used to elucidate the adhesion mechanism, through examination of fracture surfaces, resin tag length measurements, and depth of resin penetration into the dentin. Results will be compared with commercial systems.